Approximately 15 million Americans suffer in varying degrees from different forms of asthma. In 1990 alone, nearly 6.2 billion dollars were spent in total in the United States on asthma-related costs. Approximately 2 billion dollars of this amount were spent on in-patient hospital and emergency room services, and approximately 2.6 billion dollars on indirect costs such as loss of work, child care and premature death. See K. B. Weiss, P. J. Gergen and T. A. Hodgson, "An Economic Evaluation of Asthma in the United States," New Eng. J. Med., vol. 326, pp. 862-866 (1992). Despite advances in the treatment of asthma, the morbidity and mortality of the disease has increased significantly during the past several years. Moreover, asthma continues to present significant management problems for patients trying to cope with the disease on a day-to-day basis and for physicians providing medical care and treatment.
A common problem in assessing the severity of asthmatic symptoms is that patients frequently misperceive and underestimate the severity of airway obstruction. See E. R. McFadden, R. Kiser and W. J. De Groot, "Acute Bronchial Asthma: Relations Between Clinical and Physiological Manifestations," New Eng. J. Med., vol. 288, pp. 221-225 (1973); A. R. Rubinfeld, "Pain MCF: Perception of Asthma," The Lancet, pp. 882-884 (1976). Consequently, in-home monitoring of asthmatic symptoms, combined with patient education, has been shown to significantly reduce the incidence of asthma exacerbation and subsequent hospitalization. See "Li JTC. Home Peak Expiratory Flow Rate Monitoring in Patients With Asthma.," Mayo Clin. Proc., vol. 70, pp. 649-656 (1995).
In-home monitoring of asthma severity is especially useful for detecting diminished lung function before serious respiratory symptoms become evident. See R. Beasley, M. Cushley and S. T. Holgate, "A Self-Management Plan in the Treatment of Adult Asthma," Thorax, vol. 4, pp. 200-204 (1989). By identifying diminished lung function before clinical symptoms develop, a patient or physician may intervene so as to prevent worsening of a condition which may otherwise result in hospitalization or death. As such, the Expert Panel of National Asthma Education and Prevention Program considers ongoing monitoring of pulmonary function as an essential part of asthma management.
Although effective for managing and treating asthma, the reliability and accuracy of conventional in-home monitoring systems are limited by several factors. First, conventional in-home monitoring systems do not allow physicians to review and assess test results in a timely manner. Even the most advanced conventional systems, which gather peak flow data, only allow physicians to download and review patient data on a monthly or weekly basis. Still others allow patients to fax peak flow data used to generate reports that are reviewed monthly by the physician. Conventional in-home monitoring systems do not allow the timely and reciprocal exchange of patient data and medical advice between the physician and the patient, and provide no means for notifying the physician or patient of any changes in peak flow trends that occur between scheduled reports. As such, if an ominous trend or asthma exacerbation occurs between downloads or other information exchange, conventional in-home monitoring systems do not allow physicians to recognize potential problems or intervene until after the monthly or other periodic report has been generated and reviewed.
Second, conventional in-home monitoring systems completely rely on the patient's ability to properly perform and document the tests. Conventional systems do not provide automated tools for assessing the patient's compliance, and do not provide capabilities for providing meaningful reciprocal data exchange between the patient and the physician as the test is being performed.
Third, conventional systems use simple, unsophisticated and frequently inaccurate methods for evaluating the severity of asthmatic symptoms. For example, conventional systems rely on peak expiratory flow ("PEF") measurements to evaluate asthma severity. Although easy to administer, the accuracy of PEF tests can vary largely from patient to patient. This is so because the accuracy of the PEF measurements depend largely upon the patient's effort and the strength of his' or hers' expiratory muscles. In fact, several studies have shown the presence of persistent airway obstructions in asymptotic children and adults having seemingly normal PEF'S. See A. C. Ferguson, "Persistent Airway Obstruction in Asymptomatic Children With Asthma With Normal Peak Expiratory Flow Rates," J. Allergy Clinical Immunology, vol. 82, pp. 19-22 (1988); C. H. Chiang and K. Hsu, "Residual Abnormalities of Pulmonary Function in Asymptomatic Young Adults Asthmatics with Childhood-Onset Asthma," J. Asthma, vol. 34, pp. 15-21, (1997).
By contrast, the Forced Vital Capacity test ("FVC"), which requires sophisticated computerized analysis, has been shown to be a more precise test for evaluating asthma severity. The FVC test is also better than PEF tests for assessing the degree of small airways resistance. See R. E. Hyatt and L. F. Black, "The Flow Volume Curve," Am. Rev. Resp. Dis., vol. 107, pp. 191-199 (1973). In short, the same study also concluded that FVC tests provide the most reliable assessment of airway dysfunction in asthmatics. See id.
And lastly, conventional in-home monitoring systems do not provide computerized clinical decision support tools for processing and evaluating test data, thus leaving physicians with voluminous data which is very difficult to analyze in a timely and effective manner. Moreover, conventional in-home monitoring systems do not provide means for alerting the patient, in a real-time manner, of potentially serious respiratory conditions the may require immediate treatment and/or hospitalization.
As such, asthma continues to present significant management problems for patients attempting to cope with the disease on a day-to-day basis and for the physicians guiding and advising them. For the reasons noted above, conventional in-home monitoring systems and methods are limited and remain largely inadequate.